Conventionally, sheet feeding device provided in an image forming apparatus, such as a copier, a printer, a facsimile machine, or a multifunction machine having these functions, is configured to use a registration sensor to detect a feed failure jam caused by a failure to supply a sheet to a sheet path. The registration sensor is provided in the vicinity of registration rollers for correcting skew of the fed sheet and positioning the sheet properly. If the registration sensor does not detect a sheet within a predetermined time after the start of a sheet feeding operation, it is determined that the sheet has been misfed.
In recent years, shorter intervals between sheets in a continuous print job is sought to deal with faster operating speeds and improved productivity. At the same time, however, if the trailing end of a preceding sheet is overtaken by the leading end of a subsequent sheet, the sheets are conveyed together. As a result, the registration sensor fails to turn off with predetermined timing, and thus a sheet jam occurs. To prevent the leading end of the subsequent sheet from overtaking the trailing end of the preceding sheet, therefore, it is desirable to check the state of the preceding sheet, such as the position and the presence or absence thereof, before the start of the sheet feeding operation.
In the background sheet feeding device described above, which detects a misfeed using the registration sensor, however, the state of the preceding sheet is not checked before the start of the sheet feeding operation. It is therefore difficult to feed sheets while preventing the preceding sheet and the subsequent sheet from coming into contact with each other and, at the same time, reducing the intervals between the sheets. Thus, it is difficult for the above-described configuration to deal with the increase in operating speed and the improvement in productivity of image forming apparatuses.